In large scale SMRs, approximately 50% of thermal energy input from burners is transferred to SMR reforming tubes to provide energy to drive the endothermic steam methane reforming reaction, CH4+H2O+206 kJ/molCO+3H2 to produce a syngas (CO+H2). Since the reforming reaction is generally carried out at a high temperature (e.g., 750° C. to 950° C.) the temperature of a flue gas from the burners is generally at this temperature or above. Currently, the main usages of the high temperature flue gas are to generate steam through a waste heat boiler or a flue gas boiler and/or to preheat combustion air. The steam may be used as a process steam for the SMRs and/or an export steam to customer. The steam may also be used to drive a generator depending upon the local requirements which may vary from site to site. One of the challenges for optimal design and operation of a SMR is that the demand for Hydrogen may be decoupled from the demand for the export steam from a reformer. Many refiners have little or no use for the export steam generated in a hydrogen plant, which is therefore considered of low value. In case steam value is very low and natural gas price is relatively high, it is desirable to utilize the excess energy in the flue gas stream and the syngas stream for other applications other than generating steam.
U.S. Pat. No. 8,187,363 issued to Grover, et al. discloses a method of pre-heating of pressure swing adsorber (PSA) tail gas using low level waste heat in the flue gas or syngas prior to introduction into the SMR furnace combustion system. However, Grover does not disclose a detailed implementation and does not disclose a method of pre-heating of fuel gas.